1. Field of the Invention
The present invention relates to a component-built-in wiring board in which a component is accommodated in an open-ended housing portion of a core material.
2. Description of Related Art
Conventionally, a package for mounting a semiconductor element, such as LSI, has been widely employed. A typical package structure has been known as a wiring board having a laminated portion in which conductor layers and insulating layers are alternately laminated on upper and lower surfaces of a core material. Such a wiring board serves as an intermediate substrate which electrically connects an external board with a semiconductor element. In recent years, a component-built-in wiring board has been disclosed in which a component is accommodated in a housing portion of the wiring board. For example, when a via array type capacitor is accommodated in the housing portion that extends through the wiring board and when a power-supply voltage supplied to a semiconductor element is connected to the capacitor, a wiring distance between the capacitor and the semiconductor element can be reduced. Further, stabilization of the power-supply voltage and the effect of noise reduction can be enhanced.
Normally, when manufacturing a component-built-in wiring board, an opening extending through a core material is formed so as to serve as a housing portion for accommodating a capacitor therein. The capacitor is fixed in the housing portion by filling a gap between an inner circumferential portion of the housing portion and an outer circumferential portion of a component with resin filler. In the manufacturing process of the component-built-in wiring board, when a variation in temperature which originates from, for example, a soldering joint or the like arises, stress resulting from difference in the coefficient of thermal expansion between the core material and the capacitor occurs. When the core material and the capacitor are relatively deformed by such stress, the resin filler disposed therebetween can absorb such deformation. Normally, since the housing portion of the core material and the capacitor both assume a rectangular shape in a plane view, the stress tends to be concentrated at near the respective corners formed by each side of the housing portion and that of the capacitor intersecting at 90 degrees, compared to the stress generated around a straight portion of each side. Such local stress concentration potentially causes a crack or air bubbles in a portion of the resin filler. Therefore, a technique has been conventionally disclosed in which corners of the housing portion of the core material and those of the capacitor both of which assume a plane shape are chamfered in order to avoid stress concentration (Patent Documents 1 and 2).
3 Related Art Documents
Patent Document 1 is Japanese Patent Application Laid-Open (kokai) No. 2006-253668.
Patent Document 2 is Japanese Patent Application Laid-Open (kokai) No. 2002-124749.